In my opinion it's because China is a big target for Western propaganda.

The truth is that Western nations are still quite sophisticated in how their propaganda is spread. You can see this with the type of colonial mentality that some Asian nations have, where they inherently believe that anything from the West is "better."

It's quite insidious when you have a group of self-loathing people because they grew up feeling inferior.

So I can definitely see why China wants to fight against this.